The present invention is drawn to freeze drying technology. More particularly, the present invention is drawn to an improved freeze dryer.
Preservation methods have long been the subject of human study. In fact, since the beginning of recorded history, man has struggled to find methods of preservation suitable to the long term storage of goods and other objects. The many methods developed include mummification which was essentially perfected by the Egyptians, freeze drying (also referred to as lyophilization) which was initially developed by the Ancient Indians of the High Andes Mountains. In addition, modern man has developed a variety of preservation techniques including chemical preservation, mechanical refrigeration, cryogenic preservation and dehydration.
Conventional freeze dryers require a vessel which is suitable for holding a specimen to be freeze dried under low pressure (or vacuum) conditions. The freeze dryer also includes a condenser surface which maintains a condensing surface temperature cold enough to create, and collect, vapor which the specimen yields throughout the sublimation process. Finally, conventional freeze dryers require a vacuum pumping system which has enough capacity to reduce the pressure in the vessel (or chamber) quickly, and to maintain low pressure (or high vacuum) conditions throughout the freeze drying cycle.
Prior freeze dryers have typically been very large metal freeze dryers which cost a great deal to run, and which had very long drying times. Significant advantages over such large metal systems were obtained by two freeze drying systems introduced by Applicant a number of years ago. The freeze drying systems were commercially referred to as the Sani-Dry.TM. Freeze Dryer and the Taxi-Dry.TM. Freeze Dryer. Both freeze drying units include a translucent freeze drying chamber which is connected to a remote condenser which is, in turn, connected to a vacuum pump. The remote condenser is typically filled with dry ice which maintains a condensing surface in the condenser at a temperature cold enough to condense and collect vapor yielded by the specimen to be freeze dried during the sublimation process. The vacuum pump is suitable for creating a vacuum within the freeze drying chamber. In addition, the translucent chamber allows energy to be injected into the system simply by utilizing a radiant light source.
However, all of the methods currently used suffer from disadvantages. The disadvantages associated with conventional freeze drying systems include the cost of freeze drying equipment, and the associated operating expenses, as well as excessive drying times with conventional large metal equipment. In addition, conventional freeze dryers include a freeze drying chamber which is fixed in one position. Therefore, the freeze drying chamber is unsuitable for accommodating some specimens requiring a particular orientation. Also, conventional freeze dryers incur difficulty in maintaining the specimen to be freeze dried in a solidly frozen state. Further, the operating expenses of conventional freeze dryers typically are quite high because the material used in cooling the condenser surface is commonly quite expensive. In addition, there is no practical means of controlling the amount of energy supplied to conventional systems in an efficient manner. Therefore, conventional freeze dryers suffer from widely varying controllability.